- Creates new category sequence for stream network instead of original. It may
be usefull for calculating pixel position in ordered network (i.e Strahler or
Horton). By defualt it use original category of streams
- Stream network: name of input stream map on which calculation are be
performed produced by r.watershed, r.stream.extract or r.stream.order. Because
streams network produced by r.watershed and r.stream.extract may slighty differ
in detail it is required to use both stream and direction map produced by the
same module. Stream background shall have NULL value or zero value.
Background values of NULL are by default produced by r.watershed,
r.stream.extract and r.stream.order. If not 0 or NULL use r.mapcalc to set background values to null.
- Flow direction: name of input direction map produced by r.watershed or
r.stream.extract. If r.stream.extract output map is used, it only has non-NULL
values in places where streams occur. NULL (nodata) cells are ignored, zero and
negative values are valid direction data if they vary from -8 to 8 (CCW from
East in steps of 45 degrees). Direction map shall be of type CELL values. Region
resolution and map resoultion must be the same.
Also stream network map must have the same resolution. It is checked by
default. If resolutions differ the module informs about it and stops. Region
and maps boundary may be differ but it may lead to unexpected results.
- Integer used to multiply stream category for cells output map. Default is
1000. To store in one file both origial stream category and current pixel
position the stream category is multipied by multipier and next current cell
position is added.
For typical network, where stream segments are below 1000 cells such multipier
seems to be enough. For bigger networks or ordered networks may be to small in
that multiper shall be increased to larger number: 10000 or 100000. Wrong
multipier (ie not power of 10) do not stop calculation but may lead to wrong
At least one output map is required:
- Name of integer map storing both original (or new) stream category and
current pixel downstream position according formula
category * multipier
- Name of floation point map storing current pixel upstream distance (in map
units) to the begining of the stream. Categoy is not stored.
Module r.stream.pos is typical helper module which can be used to fine-tune
investigation on stream network at pixel scale and linear geostatistics. Module
can be used together with other GRASS modules and R-CRAN to investigate local
geomorphometric properties at any stream position.
For limiting oputput size, cells stores two informations in one file. To recive
current pixel stream category use (in R-CRAN) function
multipier), where multipier is the multipier value used in r.stream.pos
calculation. To recive current pixel position in segment use modulo operator:
cell %% multipier. The lengths map store only upstream distance in
map units from current pixel to the stream begining.
Module can work only if direction map, stream map and region map has same
settings. It is also required that stream map and direction map come from the
same source. For lots of reason this limitation probably cannot be omitted. This
means if stream map comes from r.stream.extract also direction map from
r.stream.extract must be used. If stream network was generated with MFD method
also MFD direction map must be used.
Last changed: $Date$